Gas-based, cook top appliances generally include a device for igniting the gas fuel once a valve is opened to supply fuel to the gas burner. One type of igniter relies on the generation of a spark to ignite the fuel. The spark is created electrically through a voltage discharge between two conductors positioned near the burner. Another type, commonly referred to as a hot surface igniter, relies on generating sufficient heat on its surface to ignite gas supplied to the gas burner. Typically, the hot surface is made of a ceramic material.
Unfortunately, hot surface igniters can be extremely fragile as the ceramic construction can be very brittle. For applications in e.g., ovens, air heating systems, water heaters, and fireplaces, the igniter can be isolated from the consumer or otherwise easily protected. However, in applications such as a cook top appliance, the fragility of the hot surface igniter can present challenges as the igniter is subject to impact during use and can be more susceptible to contamination than a spark igniter. Impacts during use or cleaning can damage the igniter and require repairs or other servicing.
Additional challenges are also presented with the use of hot surface igniters on cook top appliances. Aesthetic considerations—i.e. the shape and color of the flame created by the burner—are important to consumer perception. The placement of a device near the burner has the potential to change the shape and/or color of the flame. Preferably, the flame is somewhat symmetrical and appears mostly blue in color. The placement of an igniter in the gas flow can cause the flame to lose symmetry and/or burn with a yellowish color—which can be undesirable to some consumers.
Also, modern gas burners typically must operate over a wide range of heat outputs. For example, a gas burner may be required to operate at outputs as high as 20,000 BTU/hour while also operating in a stable manner at outputs as low as 450 BTU/hour. This range is much greater than required for the previously described applications for a hot surface igniter. As the igniter must be capable of igniting the gas fuel at both ends of this range, the igniter must be located near the source of gas fuel in order to be able to provide ignition at low flow rates. However, at high flow rates, the close proximity to the igniter negatively impacts the aesthetic considerations previously mentioned. The presence of the igniter at high gas flow tends to spread out the fuel and cause a large local plume near the igniter. Adding shielding to protect the igniter can exacerbate this aesthetic issue.
Accordingly, a hot surface igniter for the gas burner assembly of a cook top appliance would be useful. More specifically, a hot surface igniter that includes shielding for protection from breaking or other damage would be beneficial. Such an igniter that can also operate at a wide range of gas flows and properly ignite the fuel without unacceptably affecting the appearance of the flame would also be particularly useful.